Copolymers of vinylsulfonic acid salts and allylsulfonic acid salts

ABSTRACT

New copolymers have been prepared from the salts of ethenesulfonic acid and the salts of 2-propene-1-sulfonic acid by solution polymerization methods such as batch or delay. The copolymers have been found useful as dispersants for the clays used in paper coating and in latex stabilization.

United States Patent 91 Puskas Aug. 28, 1973 [7 5] Inventor: Joseph EmilPuskas, Yardville, NJ.

[73] Assignee: Sybron Corporation, Rochester,

[22] Filed: Dec. 10, 1971 [21] Appl. No.: 206,858

[52] US. Cl 260/29.65 Q, 260/79.3 MU [51] Int. Cl. C08! 15/02, C08f37/00 [58] Field of Search 260/29.6 SQ, 79.3 MU

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 842,048 6/1952Germany Primary Examiner-Melvin Goldstein Att0rneyThe0dore B, Roessel [57 ABSTRACT New copolymers have been prepared from the salts ofethenesulfonic acid, and the salts of 2-propene-lsulfonic acid bysolution polymerization methods such as batch or delay. The copolymershave been found useful as dispersants for the clays used in papercoating and in latex stabilization.

10 Claims, No Drawings BACKGROUND OF THE INVENTION lenesulfonic acid maybe used interchangeably, and lo 2-propene-1-sulfonic acid andallylsulfonic acid may be used interchangeably. Furthermore, the saltmay be designated as ethenesulfonic acid salt, allylsulfonic acid salt,and the like, or may be designated as the corresponding sulfonates, suchas, sodium allylsulfonate, potassium vinylsulfonate and the like.

Vinylsulfonic acids have been polymerized to translucent, colorlesspolymers in U. S. Pat. No. 2,515,714. The polymerization disclosedtherein is carried out with monomer free of impurities in the absence ofoxygen to render the homopolymers formed thereby colorless. Homopolymersand copolymers of sodium ethylene sulfonate are disclosed by Breslow andKutner in J. Polymer Science XXVII, 295-312 (1958). Breslow and Kutnerform copolymers of sodium ethylene sulfonate and acrylamide, sodiumethylene sulfonate and N- allylacrylamide, sodium ethylene sulfonate andacrylic acid, sodium ethylene sulfonate and methacrylic acid, sodiumethylene sulfonate and acrylonitrile and sodium ethylene sulfonate andsodium acrylate. Breslow and Kutner report that no copolymers could beprepared with sodium ethylene sulfonate and butadiene, isobutylene,styrene, alpha-methylstyrene, n-butyl vinyl ether, allyl alcohol,N-allylacetamide, maleic acid or fumaric acid. Sodium ethylene sulfonateis disclosed as a typical sulfonated olefin monomer in U. S. Pat. No.3,415,870 where it is indicated that such monomers are primarilyemployed in the preparation of homopolymers and copolymers with otherfunctional monomers.

In U. S. Pat. No. 2,974,123 and U. S. Pat. No. 2,527,300 the alkalimetal salts of both ethylenesulfonic acid and allylsulfonic acid areused as monomers in forming copolymers with other monomeric materials.Copolymers of acrylonitrile and the alkali metal salts ofethylene-sulfonic acid and acrylonitrile and the alkali metal salts ofallylsulfonic acid are prepared in U. S. Pat. No. 2,974,123. In U.S.Pat. No. 2,527,300 the sodium or potassium salt of ethylenesulfonic acidor 2-propenesulfonic acid are polymerized with a polymerizablepoly-unsaturated organic material to form a copolymer suitable for awater-insoluble cation exchange resin.

Copolymers of a salt of a 3-4 carbon allylic sulfonic acid and vinylesters of a carboxylic acid such as, vinyl acetate, vinyl formate, vinylpropionate or vinyl butyrate, have been prepared in U. S. Pat. No.2,834,759.

Thus, copolymers of the salts of ethylenesulfonic acid and acrylamide,N-allylacrylamide, acrylic acid, methacrylic acid, acrylonitrile, orsodium acrylate have been prepared. Copolymers of the salts ofallylsulfonic acid and vinyl esters of a carboxylic acid orpolymerizable poly-unsaturated materials have also been prepared.However, copolymers of the salts of ethylene sulfonic acid and the saltsof allylsulfonic acid have not been prepared heretofor.

OBJECTS OF THE INVENTION Accordingly, it the main object of thisinvention to provide a copolymer of the salts of ethylenesulfonic acidand the salts of allylsulfonic acid.

Although homopolymers of sodium salts of ethylenesulfonic acid areuseful as dispersants, for example, as dispersants for clay in anaqueous medium, their use is limited by the expense of the monomericmaterial. Monomeric sodium allylsulfonate is considerably less expensivethan sodium ethylenesulfonate, but it does not homopolymerize by thefree radical mechanism (pages 172-173 Principles of Polymer Chemistry byP. J. Flory, Cornell University Press [1953]). A polymeric materialhaving the dispersant function of the homopolymer of sodiumethylene-sulfonate and the economic advantage of sodium allylsulfonateis highly desirable.

Accordingly, it is an object of this invention to provide an economicalpolymeric material of ethylenesulfonate salts which is useful as adispersant.

Other objects of the present invention and advantageous features thereofwill become apparent to those skilled in the art.

SUMMARY OF THE INVENTION It has been found that highly desirablewater-soluble dispersing agents can be obtained by copolymerizingvinylsulfonate salts and allylsulfonate salts. The copolymers of thisinvention are obtained by the copolymerization of these salts in aweight ratio of vinylsulfonate salts to allylic sulfonate salts ofbetween about :5 and 25:75.

The copolymers of this invention, preferably in the form of an aqueoussolution, are a hygroscopic crystalline material and may be representedby the following structural formula:

wherein X is a cation selected from the group consisting of alkalimetal, alkaline earth metal and ammonium, and the weight ratio of x to yis between about 95:5 and 25:75. A particularly preferred embodiment ofthe invention is the sodium vinylsulfonate/sodium allylsulfonatecopolymer having a weight ratio of between about 40:60 and 60:40.

The cation, X, is suitably one such that the copolymer containingsulfonate groups is water soluble. The copolymer may be in the form ofsuch salts as sodium, potassium, magnesium, calcium, barium, ammonium,or the like, and mixtures thereof. The viscosity of the copolymersobtained during the polymerization in either water or an inert, inactiveliquid medium is dependent upon the amount of water or other inactive,inert liquid medium used in the reaction mixture, but it is preferredthat the viscosity of the aqueous copolymer of the present inventionfall within the range of about 2.25 cst. to 4.50 cst at 30C.

The vinylsulfonic acid salt and the allylsulfonic acid salt arecopolymerized in solution by free radical initiators.

DESCRIPTION OF THE PREFERRED EMBQDIMENT The copolymers formed inaccordance with the present invention preferably remain in the aqueoussolution in which they are prepared. However, when the copolymers areisolated from the solution in which they are prepared, they are isolatedin the form of hygroscopic crystals. The crystalline form of thecopolymers may be prepared by techniques known in the art, such as,precipitation from the aqueous solution with an alcohol, e.g., methanol,or by evaporation of the water from the aqueous solution, or by freezedrying.

Although the preferred form of the copolymers of the present inventionis the sodium salt of the vinylsulfonic acid and the sodium salt ofallylsulfonic acid, the potassium salts, barium salts, calcium salts andammonium salts, or mixtures thereof with each other or with the sodiumsalts may be easily prepared from the corresponding salts of themonomers or mixtures thereof. Accordingly, the copolymer of the presentinvention may be prepared from the alkali metal salts, such as, sodiumand potassium, of the corresponding mono mers, from the alkaline earthmetal salts, such as, barium, magnesium and calcium, of thecorresponding monomers, and from the ammonium salts of the correspondingmonomers.

Although it is preferred that the weight ratio of the salts ofvinylsulfonic acids and the salts of allylsulfonic acids be present in aweight ratio of between about 95:5 and about 25:75, it is possible toprepare copolymers containing proportions of the salts of vinylsulfonicacid and the salts of allylsulfonic acid in proportions greater than 95parts by weight of the salts of vinylsulfonic acid and less than 5 partsby weight of the allyl sulfonic acid. It is particularly preferred thatthe salts of vinylsulfonic acid and the salts of allylsulfonic acid bepresent in the water-soluble copolymer in a weight ratio of betweenabout40z60 and 60:40. Copolymer compositions containing greater thanabout 70 parts by weight of the salts of allylsulfonic acid aredifficult to prepare due to the difficulty in initiating thecopolymerization reaction, resulting in the failure of substantialportions of the monomers to copolymerize and causing a substantialportion of the monomers to remain unpolymerized.

The conversion of the monomers to the copolymers of the presentinvention can be monitored by titrating the reaction mixture or theproduct for the presence of unsaturation (double bonds) with Wyssolution by using techniques and solutions well-known in the art. Thedisappearance of the double bonds or unsaturation and the increase inthe kinematic viscosity of the solution are taken as an indication ofcopolymer formation.

The copolymerization of the salts of vinylsulfonic acid and the salts ofallylsulfonic acid may be carried out by the usual solutionpolymerization methods, such as, batch or delay, well-known to thoseskilled in the art. When proportions of the sulfonate monomers of thepresent invention are used within the ranges disclosed herein, titrationwith Wys solution indicates that upon completion of the copolymerizationonly about 1-2 percent unsaturation remains in the reaction mixture.Accordingly, nearly all of the monomer used in the formation of thecopolymer is converted to copolymer.

The copolymers of the present invention have relatively low molecularweights and accordingly, are water-soluble. Furthermore, since all unitsof the monomer structure contain sulfonate groups, the compounds remainextremely polar, a factor which contributes to water solubility of thecopolymer. Thus, the copolymerization of a sulfonate monomer of thepresent invention with another sulfonate monomer of the presentinvention produces a low molecular weight, watersoluble copolymer.

Combinations or mixtures of the sulfonate monomers may be prepared inaccordance with the present invention, for example, the sodium salt ofvinylsulfonic acid may be copolymerized with the calcium salt ofallylsulfonic acid; a mixture of the sodium and potassium salts ofvinylsulfonic acid may be copolymerized with a mixture of the sodium andpotassium salts of allylsulfonic acid; a mixture of sodium and ammoniumsalts of vinylsulfonic acid may be copolymerized with the calcium saltof allylsulfonic acid; and the like. It is within the purview of oneskilled in the art to employ mixtures of the various sulfonate salts toform the copolymers of the present invention.

Since standard polymerization techniques are used to prepare thecopolymers of the present invention, one skilled in the art may selectproper catalyst, polymerization medium and other polymerizationadditives to prepare the copolymers of the present invention. Potassiumpersulfate is the preferred catalyst, however, other free radicalgenerating catalysts, such as, ammonium persulfate and sodiumpersulfate, peroxy catalysts such as, hydrogen peroxide and benzoylperoxide including combinations of a peroxide with a reducing agent, andthe like, may be used in the polymerization reaction. Azonitn'lecatalysts may also be used as initiators. The polymerization is usuallycarried out in a homogeneous system. The reaction may be carried out inany medium which will not adversely effect the formation of thecopolymers. For example, the polymerization may be carried out in water,dimethylsulfoxide, and other solvents which will not react with thecopolymer or monomers or result in the inhibition of the polymerizationreaction by the free radical mechanism, and such polymerization isreferred to herein as a solution polymerization.

The copolymer is generally prepared in an aqueous medium and preferablyhas a solids content of 20-40 percent solids. The solids content as usedherein refers to total solids and includes the copolymer, sodiumsulfate, chlorides, catalyst fragments, and the like. It is deemedwithin the skill of one in the art to adjust the reaction proportionsand conditions to vary the solids content of the reaction mixture andproduct formed therein.

In the preferred polymerization method of the present invention 25percent of the vinylsulfonate salt in water and 25 percent of theallylsulfonate salt in water are mixed in the presence of a sufl'icientamount of a free radical catalyst. By a sufficient amount of freeradical catalyst is meant that amount of catalyst required to promotethe oopolymerization of the monomeric materials, an amount which can bedetermined by one skilled in the art. The concentration of theallylsulfonate salt and vinylsulfonate salt which can be added to thereaction mixture, may be from about 5 percent to about 70 percent ofactive monomer, the remainder of the material being water or any otherinactive, inert solvent suitable for carrying out the reaction.Accordingly, the term active vinylsulfonate salt or activeallylsulfonate salt is used herein to designate the concentration of theallylsulfonate salt or vinylsulfonate salt in either water or otherinert, inactive solvents. The maximum concentration of monomer in wateror other inert, inactive medium is generally limited to the amount ofmonomer which may be added to the medium before precipitation of themonomer occurs.

The time and temperature of polymerization are interdependent variablesand are generally selected with regard to the temperature chosen and theactivity of the initiator at that particular temperature. Thepolymerizations are usually carried out at temperatures of about 100 Cfor about 2 to 24 hours or longer. It is preferred that the reaction becarried out under nitrogen or other inert atmosphere at temperaturesrang ing from about 4585 C. depending upon the catalyst used in thereaction mixture. Thus, when potassium persulfate is used as thecatalyst, it is preferred that the reaction temperature be from about 55C. It is generally preferred that the maximum reaction temperature notexceed the boiling point of the mixture of monomers in water or otherinert, inactive medium. The reaction must be carried out for at least 2hours, and it is preferred that when potassium persulfate is used as thecatalyst at a batch temperature of 80 C., that the reaction be carriedout for approximately 6-7 hrs. The length of time at which the reactionis maintained at an elevated temperature can be determined by oneskilled in the art.

The invention is illustrated by, but not limited to, the followingexamples.

EXAMPLES The properties of the monomers used in the examples of thepresent invention are set forth below:

Sodium vinylsulfonate may. 25 min. Solids, 35: 1 Density, glml 1.20:0.02Kinematic Viscosu'y (C), est 1 60 Principal Impurities Sodiumisethionate Sodium sulfonate Sodium allylsulfonate Assay, 26.6 Solids,42.7 Density, g/ml 1.27 Kinematic Viscosity (30C.),cst 2.66 Principlelmurity Sodium chloride EXAMPLE 1 Color pale yellow Solids 37.5%Kinematic Viscosity (30C) 2.97 cst Density 1.31 glml EXAMPLE 2 Threehundred grams of 25 percent active sodium vinylsulfonate (in water), 700grams of 25 percent active sodium allylsulfonate (in water) and 1.8grams K S O were placed in the equipment described in Example 1. Thebatch temperature was raised to 80 C. under a nitrogen blanket and 1.8grams of K 8 0; per hour were added for 12 hours. After 13 hours thebatch was cooled. The water-soluble 30:70 (SVSzSAS) weight ratiocopolymer had the following properties:

Color pale yellow Solids 34.0% Kinematic Viscosity( 30C) 1 2.66 cstDensity 1.31 g/ml EXAMPLE 3 Three hundred grams of 25 percent activesodium vinylsulfonate (SVS) (in water), 300 grams of 25 percent activesodium allylsulfonate (SAS) (in water) and 1.8 grams K 8 0 were placedin equipment described in Example 1. The batch temperature was raised to80 C under a nitrogen blanket and 1.8 grams of K S O per hour were addedfor 5 hours. The batch was cooled after 6 hours. The water-soluble :30(SVS:SAS) weight ratio copolymer had the following properties:

Color pale yellow Solids 36.0 Kinematic Viscosity (30C) 2.77 cst Density1.28 glml EXAMPLE 4 One thousand eighty grams of 25 percent active SVSin water and 1.8 grams K S O were placed in equipment described inExample 1. The batch temperature was raised to C under a nitrogenblanket and 1.8 grams of K 8 0, were added at 1 hour intervals for 3hours. The batch was cooled after 3% hours. The water-solublevinylsulfonate homopolymer had the following properties.

Color pale yellow Solids 37.0 Kinematic Viscosity (30C) 3.34 cst Density1.25 gloc.

EXAMPLE 5 Color e ellow Solids pal 37.5% Kinematic Viscosity (30C) 2.68Density 1.27 glcc EXAMPLE 6 Seven hundred grams of 25 percent active SVS(in water), 300 grams of 25 percent SAS (in water) and 1.8 grams K,S,Owere placed in equipment described in Example 1. The batch temperaturewas raised to 60 C under a nitrogen blanket and 1.8 grams of K 8 0; wereadded at 1 hour intervals for 5 hours. The batch Color pale yelllowSolids 37.0% Kinematic Viscosity (30C) 3.07 at Density 1.27

EXAMPLE 7 v The dispersing ability of the product was determined 7 bythe length of time it could hold clay in suspension.

The test was carried out as follows:

Two grams of clay (Hydrogloss 90) were added to 60 cc of demineralizedwater in a 100 cc graduated cylinder, shaken and permitted to standminutes. Various concentrations of product were added, diluted withdemineralized water to 100 cc, inverted 12 times to mix, and placedagainst a dark background. A timer was started and stopped when theclay-water interphase reached the 30 cc mark. The time it took the clayto settle from the 100 cc mark to the 30 cc mark was used as a basis forcomparison. The table below shows the results of these measurements:

TABLE 1 Clay Dispersing Ability Of SVS/SAS Compolymers" Sample SVSzSAS,k ppm Time sec. Blank no copolymer 245 Example 4 SVS Homopolymer Example6 70:30 011 305 0.4 290 -Examle l 50:50 0.l 286 0.4 276 Example 5 30:700.1 320 0.4 3l9 pH 5-6 I *temperature=ambient The data in table 1indicate that the copolymers of the present invention have claydispersing ability as good as that of the sodium vinylsulfonatevhomopolymer.

EXAMPLE 8 The copolymers of the present invention have been found usefulas dispersants for clays, such as, the type of clay used for papercoating or as stablizers for latexes.

References to parts, proportions, or percentages refer to parts,proportions, or percentages by weight throughout the specification andclaims unless otherwise specified.

The above examples are not meant to limit the scope of the invention orthe application to which this invention may be directed. It, is to beunderstood that although the invention has been described with specificreference to particular embodiments thereof, it is not to be so limited,since changes and alterations therein may be made which are in the fullintended scope of this invention as defined by the appended claims.

I claim:

1. As a new composition of matter, a water-soluble copolymer having theformula:

wherein the weight ratio of x to y is between about 95:5 and 25:75 and Xis at least one cation selected from the group consisting of alkalimetal, alkaline earth metal and ammonium.

2. The composition of claim 1 wherein the weight ratio of x to y isbetween about 40:60 and 60:40.

3. The composition of claim 1 wherein the alkali metal is selected fromthe group consisting of sodium and potassium and the alkaline earthmetal is selected from the group consisting of barium, magnesium andcalcium.

4. Aqueous solution of the copolymers of claim 1.

5. A water-soluble copolymer consisting essentially of salts ofvinylsulfonic acid, said salts being selected from the group consistingof the alkali metal salts, the alkaline earth metal salts, the ammoniumsalt and mixtures thereof, and salts of allylsulfonic acid, said saltsbeing selected from thegroup consisting of the alkali metal salts, thealkaline earth metal salts, the ammowas cooled an hour later. The watersoluble 5:95

(SVS:SAS) weight ratio copolymer had the following properties:

Color pale yellow Solids 45.7% pIH 2.7

iscosity (30C) 4.08 centistokes (cst) Density 1.27 g/cc.

nium salt and mixtures thereof, in which the weight ratio of the saltsof vinylsulfonic acid and the salts of allylsulfonic acid is betweenabout :5 and 25:75.

6. The copolymer of claim 5 wherein the weight ratio of the salts ofvinylsulfonic acid and the salts of allylsulfonic acid is between about40:60 and 60:40.

7. The copolymer of claim 5 wherein the alkali metal salt is selectedfrom the group consisting of sodium and potassium and the alkaline earthmetal salt is selected from the group consisting of barium, magnesiumand calcium.

8. Aqueous solution of the copolymers of claim 5.

9. The aqueous solution of claim 8 wherein the weight ratio of the saltsof vinylsultonic acid and the salts of 40:60 acid is between about 40:60and 60:40.

10. The aqueous solution of claim 8 wherein the alkali metal salt isselected from the group consisting of sodium and potassium, and thealkaline earth metal salt is selected from the group consisting ofbarium, magnesium and calcium.

2. The composition of claim 1 wherein the weight ratio of x to y isbetween about 40:60 and 60:40.
 3. The composition of claim 1 wherein thealkali metal is selected from the group consisting of sodium andpotassium and the alkaline earth metal is selected from the groupconsisting of barium, magnesium and calcium.
 4. Aqueous solution of thecopolymers of claim
 1. 5. A water-soluble copolymer consistingessentially of salts of vinylsulfonic acid, said salts being selectedfrom the group consisting of the alkali metal salts, the alkaline earthmetal salts, the ammonium salt and mixtures thereof, and salts ofallylsulfonic acid, said salts being selected from the group consistingof the alkali metal salts, the alkaline earth metal salts, the ammoniumsalt and mixtures thereof, in which the weight ratio of the salts ofvinylsulfonic acid and the salts of allylsulfonic acid is between about95:5 and 25:75.
 6. The copolymer of claim 5 wherein the weight ratio ofthe salts of vinylsulfonic acid and the salts of allylsulfonic acid isbetween about 40:60 and 60:40.
 7. The copolymer of claim 5 wherein thealkali metal salt is selected from the group consisting of sodium andpotassium and the alkaline earth metal salt is selected from the groupconsisting of barium, magnesium and calcium.
 8. Aqueous solution of thecopolymers of claim
 5. 9. The aqueous solution of claim 8 wherein theweight ratio of the salts of vinylsulfonic acid and the salts of 40:60acid is between about 40:60 and 60:40.
 10. The aqueous solution of claim8 wherein the alkali metal salt is selected from the group consisting ofsodium and potassium, and the alkaline earth metal salt is selected fromthe group consisting of barium, magnesium and calcium.